From e623c5875430a38c8ceede68a2d6dc54dd0e62a3 Mon Sep 17 00:00:00 2001
From: Tyler Goodlet <jgbt@protonmail.com>
Date: Sat, 22 May 2021 11:40:54 -0400
Subject: [PATCH 1/2] Naively throttle graphics updates to 60 FPS

---
 piker/ui/_chart.py | 29 +++++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/piker/ui/_chart.py b/piker/ui/_chart.py
index 0650663c..ea1544fa 100644
--- a/piker/ui/_chart.py
+++ b/piker/ui/_chart.py
@@ -18,6 +18,7 @@
 High level Qt chart widgets.
 
 """
+import time
 from typing import Tuple, Dict, Any, Optional, Callable
 from types import ModuleType
 from functools import partial
@@ -934,7 +935,9 @@ async def test_bed(
         # txt.setPos(vb_right - w, d_coords.y())
         # txt.setPlainText(f"FUCK YOU {i}")
         i += 1
-        # rlabel.setPos(vb_right - 2*w, d_coords.y())
+
+
+_quote_throttle_rate = 60  # Hz
 
 
 async def chart_from_quotes(
@@ -1011,9 +1014,17 @@ async def chart_from_quotes(
     tick_size = chart._lc.symbol.tick_size
     tick_margin = 2 * tick_size
 
+    last = time.time()
     async for quotes in stream:
-        for sym, quote in quotes.items():
 
+        now = time.time()
+        period = now - last
+        if period <= 1/_quote_throttle_rate:
+            # faster then display refresh rate
+            # print(f'quote too fast: {1/period}')
+            continue
+
+        for sym, quote in quotes.items():
             for tick in quote.get('ticks', ()):
 
                 # print(f"CHART: {quote['symbol']}: {tick}")
@@ -1099,6 +1110,8 @@ async def chart_from_quotes(
 
                 last_mx, last_mn = mx, mn
 
+                last = now
+
 
 async def spawn_fsps(
     linked_charts: LinkedSplitCharts,
@@ -1272,9 +1285,19 @@ async def run_fsp(
 
         stream = conf['stream']
 
+        last = time.time()
+
         # update chart graphics
         async for value in stream:
 
+            now = time.time()
+            period = now - last
+            # if period <= 1/30:
+            if period <= 1/_quote_throttle_rate:
+                # faster then display refresh rate
+                # print(f'quote too fast: {1/period}')
+                continue
+
             # TODO: provide a read sync mechanism to avoid this polling.
             # the underlying issue is that a backfill and subsequent shm
             # array first/last index update could result in an empty array
@@ -1299,6 +1322,8 @@ async def run_fsp(
             # update graphics
             chart.update_curve_from_array(fsp_func_name, array)
 
+            last = now
+
 
 async def check_for_new_bars(feed, ohlcv, linked_charts):
     """Task which updates from new bars in the shared ohlcv buffer every

From 9e367432fd546138ea4e8187599832ded14633e9 Mon Sep 17 00:00:00 2001
From: Tyler Goodlet <jgbt@protonmail.com>
Date: Tue, 25 May 2021 06:56:18 -0400
Subject: [PATCH 2/2] Minimize update to Qt reported display's refresh rate

---
 piker/ui/_chart.py | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/piker/ui/_chart.py b/piker/ui/_chart.py
index ea1544fa..9f6e118b 100644
--- a/piker/ui/_chart.py
+++ b/piker/ui/_chart.py
@@ -937,7 +937,7 @@ async def test_bed(
         i += 1
 
 
-_quote_throttle_rate = 60  # Hz
+_quote_throttle_rate: int = 60  # Hz
 
 
 async def chart_from_quotes(
@@ -1019,7 +1019,7 @@ async def chart_from_quotes(
 
         now = time.time()
         period = now - last
-        if period <= 1/_quote_throttle_rate:
+        if period <= 1/_quote_throttle_rate - 0.001:
             # faster then display refresh rate
             # print(f'quote too fast: {1/period}')
             continue
@@ -1110,7 +1110,8 @@ async def chart_from_quotes(
 
                 last_mx, last_mn = mx, mn
 
-                last = now
+        # set time of last graphics update
+        last = now
 
 
 async def spawn_fsps(
@@ -1293,7 +1294,7 @@ async def run_fsp(
             now = time.time()
             period = now - last
             # if period <= 1/30:
-            if period <= 1/_quote_throttle_rate:
+            if period <= 1/_quote_throttle_rate - 0.001:
                 # faster then display refresh rate
                 # print(f'quote too fast: {1/period}')
                 continue
@@ -1322,6 +1323,7 @@ async def run_fsp(
             # update graphics
             chart.update_curve_from_array(fsp_func_name, array)
 
+            # set time of last graphics update
             last = now
 
 
@@ -1531,10 +1533,22 @@ async def _async_main(
     Provision the "main" widget with initial symbol data and root nursery.
 
     """
+
     chart_app = widgets['main']
 
     # attempt to configure DPI aware font size
-    _font.configure_to_dpi(current_screen())
+    screen = current_screen()
+
+    # configure graphics update throttling based on display refresh rate
+    global _quote_throttle_rate
+    _quote_throttle_rate = min(
+        round(screen.refreshRate()),
+        _quote_throttle_rate,
+    )
+    log.info(f'Set graphics update rate to {_quote_throttle_rate} Hz')
+
+    # configure global DPI aware font size
+    _font.configure_to_dpi(screen)
 
     async with trio.open_nursery() as root_n: